The Bill and Melinda Gates Foundation has challenged the world to reinvent the toilet and the new designs will be making their debut in Seattle.

On Tuesday, the foundation will be hosting its "Reinvent the Toilet Fair." This isn't just about getting a better working toilet or even water conservation, they're hoping the next generation of toilets will help save millions of lives.

"Good sanitation saves lives and it's really a key to good health globally. Today, 2.5 billion people don't have access to toilets and 1.5 million child deaths are attributed to poor sanitation conditions," says Carl Hensman, the Program Officer for Water Sanitation and Hygiene at the Bill and Melinda Gates Foundation. "Two-hundred years ago we had the invention of the flush toilet and we've really not done anything in the engineering of the toilet since then."

There are experts from Singapore, Switzerland, China, and the UK in Seattle for the toilet fair after the foundation introduced the challenge one year ago to reinvent the toilet.

The toilets they're looking for will work off the grid, says Hensman. The toilet should require no power, little or no water, and be able to support users for no more than 5 cents per user per day. He says they've got at least eight really promising designs.

"There are different ways of doing it. In one of the examples we have what is called 'hydrothermal carbonization,' a really big term that really represents a pressure cooker. What you do is take the fecal material and the urine and you'll essentially cook it under pressure and the material you get out of that has an energy you can use to fuel your cooker or you can actually use it as a fertilizer as well," says Hensman.

They also have a couple dozen more exhibits that will be showcased that look at things like water sanitation and recycling the water that is used in some toilets. The toilet designs will also be demonstrated for the crowds.

"We have supplied simulated feces," says Hensman. "Some of the exhibitors have brought their own fake material."

After one year, some really promising progress has been made, but Hensman says there's still work that needs to be done. He's hoping everyone can work together in a collaborative effort to find the best possible design.

"There are pieces of each of their technologies that can be combined," says Hensman. "That's what we're really looking for is how can we pull everybody together to sort the solution out."

Once they've put a solid plan together, then they'll work on a plan to roll out the new toilets. Hensman says it could be a matter of one toilet per household or even communal toilets that could be used by hundreds or even thousands of people.